Liquid Crystal Displays (LCDs) contain several layers which work in combination to create a viewable image. A backlight is used to generate the rays of light that pass through what is commonly referred to as the LCD stack, which typically contains several layers that perform either basic or enhanced functions. The most fundamental layer within the LCD stack is the liquid crystal material, which may be actively configured in response to an applied voltage/charge in order to pass or block a certain amount of light which is originating from the backlight. The layer of liquid crystal material is divided into many small regions which are typically referred to as pixels. For full-color displays these pixels are further divided into independently-controllable regions of red, green and blue subpixels, where the red subpixel has a red color filter, blue subpixel has a blue color filter, and green subpixel has a green color filter.
The light which is passing through each subpixel typically originates as “white” (or broadband) light from the backlight, although in general this light is far from being uniform across the visible spectrum. The subpixel color filters allow each subpixel to transmit a certain amount of each color (red, green or blue). When viewed from a distance, the three subpixels appear as one composite pixel and by electrically controlling the amount of light which passes through each subpixel, the composite pixel can produce a very wide range of different colors due to the effective mixing of light from the red, green, and blue subpixels.
Currently, the common and preferable illumination source for LCD backlight assemblies is light emitting diodes (LEDs). Environmental concerns, small space requirements, lower energy consumption, and long lifetime are some of the reasons that the LCD industry is beginning the widespread usage of LEDs for backlights.
LCDs are becoming popular for not only home entertainment purposes, but are now being used as informational/advertising displays in both indoor and outdoor locations. When used for information/advertising purposes, the displays may remain ‘on’ for extended periods of time and thus would see much more use than a traditional home theatre use. Further, when displays are used in areas where the ambient light level is fairly high (especially outdoors or in aircraft cockpits) the displays must be very bright in order to maintain adequate picture brightness. When used for extended periods of time and/or outdoors, durability of the components can become an issue.
Modern LCD devices have become more sophisticated and now use a plurality of sensors and logic to maintain optimal performance. As is readily apparent, an LCD will not function satisfactorily without an appropriate and properly-functioning control system. The backlight is also essential for proper functioning as the image or data displayed on the liquid crystal layer may only be viewed while the backlight is providing proper illumination to the liquid crystal stack. If the backlight system should fail completely or operate at a less than optimal level, then the LCD will not perform satisfactorily. While this may be a simple inconvenience when LCDs are used for entertainment purposes, when used for information or data displays this can be very costly. For example, LCDs are now being used in aircraft cockpits as well as the instrument panels or display(s) in ground vehicles and marine equipment. In these applications, when there is a failure within the control system, the LCD may no longer display the important information for the vehicle/aircraft and controls may cease to operate. These situations can be undesirable not only to the passengers of the vehicle/aircraft, but also other soldiers/team members who are counting on this part of the mission.
Some control systems have a limited life span, and eventually their performance may suffer. Some systems may quickly fail simply due to a manufacturing defect or may fail due to shock/forces applied to the aircraft or ground vehicle. Currently when this occurs, the entire LCD device must be manually replaced. This is expensive, and is often time consuming. Alternatively, the LCD device could be removed from the display housing, and the degraded or faulty system elements could be manually replaced. This is typically even more costly, and involves extensive manual labor. In currently known units, this also requires virtual complete disassembly of the LCD to gain access to the electronics. This complete disassembly is not only labor intensive, but must be performed in a clean room environment and involves the handling of expensive, delicate, and fragile components that can be easily damager or destroyed, even with the use of expensive specialized tools, equipment , fixtures, and facilities.
Thus, there exists a need for a more durable and dependable control system for an LCD so that failures can be accounted for and vehicles/aircraft can complete a mission and/or return safely to base.